[PATCH v4 01/23] libtuning: Backport improvements in MacBeth search reliability

[Stefan Klug]

Port commit 66479605baca ("utils: raspberrypi: ctt: Improve the Macbeth
Chart search reliability") into libtuning.

Previously the code would brighten up images in case the Macbeth Chart
is slightly dark, and also zoom in on sections of it to look for
charts occupying less of the field of view. But it would not do both
together.

This change makes the search for smaller charts also repeat that
search for the brightened up images that it made earlier, thereby
increasing the chances of success for non-optimal tuning images.

Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder at ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 utils/tuning/libtuning/macbeth.py | 38 ++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/utils/tuning/libtuning/macbeth.py b/utils/tuning/libtuning/macbeth.py
index e11824646a4f..81f3e87c9088 100644
--- a/utils/tuning/libtuning/macbeth.py
+++ b/utils/tuning/libtuning/macbeth.py
@@ -403,10 +403,15 @@ def find_macbeth(img, mac_config):
     # nothing more is tried as this is a high enough confidence to ensure
     # reliable macbeth square centre placement.
 
+    # Keep a list that will include this and any brightened up versions of
+    # the image for reuse.
+    all_images = [img]
+
     for brightness in [2, 4]:
         if cor >= 0.75:
             break
         img_br = cv2.convertScaleAbs(img, alpha=brightness, beta=0)
+        all_images.append(img_br)
         cor_b, mac_b, coords_b, ret_b = get_macbeth_chart(img_br, ref_data)
         if cor_b > cor:
             cor, mac, coords, ret = cor_b, mac_b, coords_b, ret_b
@@ -456,23 +461,24 @@ def find_macbeth(img, mac_config):
         w_inc = int(w * pair['inc'])
         h_inc = int(h * pair['inc'])
 
-        loop = ((1 - pair['sel']) / pair['inc']) + 1
+        loop = int(((1 - pair['sel']) / pair['inc']) + 1)
         # For each subselection, look for a macbeth chart
-        for i in range(loop):
-            for j in range(loop):
-                w_s, h_s = i * w_inc, j * h_inc
-                img_sel = img[w_s:w_s + w_sel, h_s:h_s + h_sel]
-                cor_ij, mac_ij, coords_ij, ret_ij = get_macbeth_chart(img_sel, ref_data)
-
-                # If the correlation is better than the best then record the
-                # scale and current subselection at which macbeth chart was
-                # found. Also record the coordinates, macbeth chart and message.
-                if cor_ij > cor:
-                    cor = cor_ij
-                    mac, coords, ret = mac_ij, coords_ij, ret_ij
-                    ii, jj = i, j
-                    w_best, h_best = w_inc, h_inc
-                    d_best = index + 1
+        for img_br in all_images:
+            for i in range(loop):
+                for j in range(loop):
+                    w_s, h_s = i * w_inc, j * h_inc
+                    img_sel = img_br[w_s:w_s + w_sel, h_s:h_s + h_sel]
+                    cor_ij, mac_ij, coords_ij, ret_ij = get_macbeth_chart(img_sel, ref_data)
+
+                    # If the correlation is better than the best then record the
+                    # scale and current subselection at which macbeth chart was
+                    # found. Also record the coordinates, macbeth chart and message.
+                    if cor_ij > cor:
+                        cor = cor_ij
+                        mac, coords, ret = mac_ij, coords_ij, ret_ij
+                        ii, jj = i, j
+                        w_best, h_best = w_inc, h_inc
+                        d_best = index + 1
 
     # Transform coordinates from subselection to original image
     if ii != -1:
-- 
2.43.0